Her parents called me last week and pleaded with me to get the kids and they SAY they will do anything to help me do that. They have met OM several times and do not want him around kids. I won't ask then for help, as it would forever tarnish their relationship with W.
Take their help. I'm serious. If this OM is as bad as they seem to think, your number one goal needs to be protecting your kids, not your wife. And be very very grateful for in-laws that are putting your kids' welfare above their loyalty to their daughter.